STUDIES ON FEKMEKTATIO^. 19 



vats, tubs, casks, shovels, workmen's clotiies, and innumerable 

 other things. 



It is evident that this proposition bears a marked resembiance 

 to the one which we have demonstrated concerning the diseases 

 of wine.* 



By the expression diseases of wort and beer, we mean radical 

 changes which so affect the nature of those liquids as to make 

 them unpalatable, especially if they are kept ; such changes 

 produce beer which is sharp, sour, turned, oily, putrid, and 

 otherwise bad. It would be unreasonable to apply the term 

 disease to certain modifications in the quality of beer, which 

 may be produced by practices more or less commendable. Such 

 modifications, too, may result from want of skill in the brewer, 

 from the composition of the wort, from the specific nature of 

 the yeast, or from the inferior quality of ingredients. It is a 

 well-known fact that " low beer," if manufactured according to 

 the ordinary process, has not that same delicacy of flavour 

 which characterizes beer fermented at a lower temperature than 

 10° C. (50° F.). Fermented at 10^ C. (50°F.),or 12^^ C. (53° F.) 

 or at a higher temperature, it loses the peculiar properties 

 which consumers prize. Nevertheless, in point of soundness it 

 may be as good a beer as one which has been fermented at 6° C. 

 (43° F.), or 8° C. (46° F.). One might say of the former beer 

 that it is inferior to the latter in estimation ; but we could not 

 rightly call it diseased, for we are supposing a case in which 

 disease does not actually exist. 



§ I. — Every Unhealthy Change in the Quality of Beer 



COINCIDES with A DEVELOPMENT OF MICROSCOPIC GeRMS 

 which are ALIEN TO THE PuRE FeRMENT OF BeER, 



Our proposition concerning the causes of the diseases of wort 

 and beer might be demonstrated in several ways. The follow- 

 ing is one of the simplest : — Take a few bottles of sound beer, 



* A statement of this proposition, as far as it concerns beer, appeared 

 first in outline in the author's Etudes sur le vin, published in 1866. 



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